Re: air con.

["Fred Munro" <munrof@isys.ca>]

I have had a similar A/C problem with both my quattros, and the cause was
the same in both cases. There is a thermal switch located under the plastic
plenum cover beside the evaporator box (passenger side). A capillary tube
mounted in the evaporator activates a microswitch which cycles the
compressor on when the evap core heats up and off when the evap core cools
down. The switch is cunningly located just under the end of the plenum cover
so that water drips on it. This invariably leads to corrosion on the switch
contacts and  the tab terminals and eventually the compressor stops cycling.
    The switch on my '91 200q was in really bad shape, so I asked the dealer
the price of a replacement. $400 - inured as I am to ridiculous Audi prices,
I nearly choked!
    Test the switch by pulling the leads and connecting them. If the
compressor runs, the switch is defective.
    The switch can be removed by unbolting it from the bracket and carefully
sliding the capillary tube out of the evap core. Don't bend the capillary
tubing! With care, the switch can be disassembled, the contacts cleaned, and
the whole thing re-assembled. The cycle temperature range is factory set
with a small threaded screw on the microswitch mechanism. Don't disturb this
setting and replace and crimp the cover plate in exactly the same position.
    The tab terminals on the switch on the 200q were corroded beyond
salvation, so I soldered two leads to them and added new tab terminals which
I tucked into a dryer location.
    This thermal switch looks suspiciously like the $60 unit on my '79 Chev
van, so a cheap replacement may be available if the repair job fails. I have
successfully repaired these switches on my '86 5kcstq and my '91 200q.

HTH

Fred Munro
'91 200q  253k km
-----Original Message-----
From: Chewy4000@aol.com <Chewy4000@aol.com>
To: mhauk@ccsdana.net <mhauk@ccsdana.net>; quattro@coimbra.ans.net
<quattro@coimbra.ans.net>
Date: Wednesday, June 03, 1998 9:17 AM
Subject: Re: air con.


>In a message dated 98-06-03 00:31:52 EDT, mhauk@ccsdana.net writes:
>
><<
> Okay, time to call upon the collective knowledge of the Qlist.  Having
> problems with getting the compressor to engage on 89 200tq.  Known: 1)
Have
> power to low pressure switch.  2) Able to engage compressor by jumping
> wires at compressor.  What we are having a problem with is the fact that
we
> cannot get voltage or find the wire for that matter that flows from the
low
> pressure switch over to ?  Is there a relay somplace for this?  Fuse box
> has a listing for (2) two relays but there has never been a relay in that
> location for as long as I remember. (Air used to work very well)
>
> Any help would be greatly and cooly :) appreciated.
>
> Thanks,
>
> Dave
>  >>
>
>You couln't have put it better Dave.
>I was about to write word for word the same damn thing.
>I was told by an Audi Dealer Shoemaker, that the 4-way sensor switch would
>solve this A/C and my Temp gauge problem.
>So I payed 4?$$$ for the switch put it in aaaannnndddd nada same 2 problems
>but 4?$ less now.
>
>Hope some one can help us.
>
>Chewy